Surfaces of molded products generally have various indications such as a date of production, lot number, product number and so on by which producers can clear up causes of inferior molded products or check their stock.
A marking device is removably inserted into a mold with its indication portion facing the inner surface of the mold and held there during molding so that the above mentioned indications carried on the indication portion can be marked on each molded product.
One conventional marking device is shown in reference 1, and the device is shown in FIG. 8. The marking device consists of a substantially cylindrical outer member (O), which mark data is marked in upper surface, a substantially volt shape indicator portion (I) of a spring (S), a nut (N), and a cover member (C).
The indicator portion (I) is fitted in the outer member (O) from upper of the outer member (O). The nut (N) is installed in the outer member (O) from its downward. The nut (N) is screwed with a thread (I1) formed lower of the indicator portion (I).
The spring (S) is located between the nut (N) and a bore portion (O1) formed in middle portion of inner wall of the outer member (O) in axial direction. The spring (S) downwardly biases the nut (N) and the indicator portion (I) connected with the nut (N). The cover member (C) is screwed with a female screw formed in lower part of the inner wall of the outer member (O). The cover member (C) closes a lower opening of the outer member (O).
In middle portion of the indicator portion (I), a projection portion (I2) which consists of a spring and a sphere protrudes in radial direction of the indicator portion (I).
Further, plural positioning grooves (O3) that a projection portion (I2) is fit circumferentially formed equally at a bore portion (O1) of the outer member (O). The number of the positioning groove (O3) is decided based on the number of characters marked on upper surface of the outer member (O).
For example, as shown in FIG. 8, numerical characters are carved in upper surface of the outer shell body (O). In case of the numbers of the numeral characteristic are 1˜12, twelve positioning grooves (O3) are carved.
A structure of the marking device described in the reference 1 is that when the indicator portion (I) is revolved, a projection portion (12) protruded from the indicator portion (I) is fit in the positioning groove (O3), an angular position of the indicator portion (I) is tightly fixed at desire position.
Reference 1 Japan Patent No. 3470880
Since the marking device described in the reference 1 has above-mentioned structure, it has reliable positioning function, but there are following problems.
In case of size of a molded product is small, a size of the marking device is also small. Therefore, length of inner circumference of the outer member is also shortens. In case of manufacture month is carved on the outer member, number of numeric characters are 12, and as mentioned above, the positioning grooves must be formed twelve.
Therefore, width of formed positioning groove narrows as decreasing size of the marking device. Narrowing of the width of the positioning groove causes decreasing of engagement with projection for positioning. As a result, reliable positioning cannot be maintained.
As a method for increasing engagement, depth of the positioning groove may be deepened, but rotation of the indicator may be hard and prevented.
Increasing of indicated numeric character carved on the outer member has similar problem.
In view of the problem of prior art's marking devices as mentioned above, the present invention provides a removable marking device having reliable positioning function, even if the size of the device is small.
According to an invention described in claim 1 and 2, when at least one of the projection portions for positioning is fit in the positioning groove, other projection portions touches to inner surface of the outer member, the indicator can be tightly fixed.
Further, the positioning groove can be decreased as the number of the projection portion decreasing, and the positioning groove having wide width can be formed, or the carved character of the outer member can increase twice.
According to the invention described in claim 3, since the nut and the indicator connected with the nut are biased downwardly with the spring, upper surface of the indicator and upper surface of outer member are in same surface, convexoconcave of marking surface can be prevented.
According to the invention described in claim 4, since an engageable projection of the nut and an engageable groove are engaged at lower part of the outer member, the nut does not rotate. Torque is not applied to the spring which touches the nut and the force is applied only in telescopic motion direction, and a damage of the spring can be prevented.
According to the invention described in claim 5 and 6, lower end of the indicator is inserted in the opening formed in the cover member, and breaking of conjunction of the nut and a thread in adjustment of marking can surely be prevented, and a thinner nut can be used.
Therefore, distance of nut's movement can be longer, and the adjustment of marking can be simply and easily.
According to the invention described in claim 7˜9, when the nut moves from lower portion to upper portion by adjusting of angular position of the indicator, movement of the nut is limited at upper end of the engageable groove. Therefore, damage of thread of the indicator can be prevented, because the nut does not engage to bottom end of the thread part of the indicator.
According to the invention described in claim 10˜18, since a hemisphere of a spherical inserted part is inserted into the positioning groove, the indicator is reliably positioned and the inserted part is not entangled in the positioning groove, damage of the positioning projection portion can be prevented.